Semiconductor device formation is commonly conducted in substrate processing platforms containing multiple chambers. In some instances, the purpose of a multi-chamber processing platform or cluster tool is to perform two or more processes on a substrate sequentially in a controlled environment. In other instances, however, a multiple chamber processing platform may only perform a single processing step on substrates; the additional chambers are intended to maximize the rate at which substrates are processed by the platform. In the latter case, the process performed on substrates is typically a batch process, wherein a relatively large number of substrates, e.g. 25 or 50, are processed in a given chamber simultaneously. Batch processing is especially beneficial for processes that are too time-consuming to be performed on individual substrates in an economically viable manner, such as for atomic layer deposition (ALD) processes and some chemical vapor deposition (CVD) processes.
Some ALD systems, especially spatial ALD systems with rotating substrate platens, benefit from a modular plasma source, i.e., a source that can be easily inserted into the system. The plasma source consists of a volume where plasma is generated, and a way to expose a workpiece to a flux of charged particles and active chemical radical species.
Some processing platforms use rotating carousels that hold multiple wafers to deposit thin films. The volume above the wafers may be partitioned into regions that are isolated from each other by a gas curtain. Each section can apply separate gas to adhere to the wafer surface and grow the film. Due to the rotation, gas flow within each section may be adjusted so that the wafer regions at different radii on the carousel receive similar treatments. Plasma sources are meant to perform in the same way; however, existing plasma source designs provide different treatments at the inner diameter of the carousel than at the outer diameter.
Therefore, there is a need in the art for plasma sources which provide increased uniformity between the inner diameter and outer diameter of the wafer in a batch processing chamber.